Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Is AUTOSPC the same as “Automatic constraints”?

Is AUTOSPC the same as “Automatic constraints”?

Is AUTOSPC the same as “Automatic constraints”?

The title seems pretty self explanatory, but the automatic constraints check box is located in “solution type” —> “solution parameters”.

And if I wanted to enable AUTOSPC through the .bdf, would that just be going to the PARAM section and adding a line for “PARAM AUTOSPC YES”?

I can’t seem to find an answer online. Thanks!

RE: Is AUTOSPC the same as “Automatic constraints”?

Yes, the automatic constraints box in Patran equates to the AUTOSPC capability in MSC Nastran.

For the linear solution sequences in the range SOL 101-200, the default for this is YES, so you don't need to add anything into the input file. If you want to define this, PARAM,AUTOSPC,YES would work, but it is deprecated for a good few versions now, and the case control AUTOSPC command should be used instead; something like:


The case control command wraps a bunch of other parameters related to AUTOSPC into a single command, so the options on the case control AUTOSPC command let you do things like suppress the singularity table, or only print non-zero stiffness ratios, etc.

For SOL 400, AUTOSPC is ignored for nonlinear steps; singularity processing occurs in the solver. For any linear perturbation steps, you must use the command


for singularity processing of the linearised problem.


RE: Is AUTOSPC the same as “Automatic constraints”?

Thanks dmapguru! That makes perfect sense.

You seem to have a deep understanding of Nastran, so I was wondering- could you possibly help answer another question I have?

Not sure if this violates posting by asking here, but do you understand what the use of a .pch file is? If it contains information about the stiffness matrices of specific nodes, can I import that data back into a patran database?


RE: Is AUTOSPC the same as “Automatic constraints”?

The short answer is "not usually". The pch file does not typically contain information about the stiffness matrices of specific nodes (GRID points). Although I know MSC Nastran very well, I am no expert in Patran, so I think I am right when I say Patran cannot read the pch file.

You asked "do you understand what the use of a .pch file is?". Yes, but first some history.

When Nastran was first conceived for NASA and subsequently enhanced into the commercial product MSC Nastran, computers at that time did not have graphics capabilities. In the late 1960's and early 70's, input to computers was prepared on cardboard cards and output appeared via dot matrix printers. The cardboard cards were called punch cards, because they had rectangular holes punched into them, each card describing a single entry in the deck of cards which make up what we now call the input file. To this day, we still refer to entries in the input file as cards and the complete input file as a deck. The cardboard cards were read by a punch card reader, but with time and abuse they could become bent or torn. As well as a punch card reader, there was a device for creating the punch cards (the puncher) which had a keyboard so you could manually create cards (hours of fun). This device could also accept input from a computer, so you could easily request an echo of some or all of your deck to be directed to the punch card puncher and obtain crisp new cards of your input. Google "Punched card input/output" on Wikipedia for the full glory.

At this time, online data (as opposed to the offline punch cards) was not stored in files as we know them, it was stored either on magnetic tape or for the high end systems, cylindrical drums. As time went by, these devices were replaced by files in filesystems, so the punch (pch) file is the modern rendition of the information that was designed to be received by a punch card puncher from an echo from the Nastran job.

People have asked "where is the format of the punch file". Well it didn't need a separate description because it was unambiguously defined by the input data, which is a documented format. With the passage of time, the pch file has taken on all sorts of functions and capabilities none of which is in the original design intent. For example, it is possible to obtain results data in the pch file (look at the DISP(PUNCH)= case control command), XY plotting data can be written therein (see the XYPUNCH plotting command). It is also used to output one of the flavours of external superelements, i.e. EXTSEOUT with the DMIGPCH option. In this case, MSC Nastran will write the boundary matrices of the external superelement (including the stiffness if you asked for it) to the pch file in DMIG bulk data format. OTM data for data recovery may also appear in the pch file.

Now I have a question. What are you trying to do when you ask if you can "import that data back into a patran database"? Patran has no way to abstract or visualise stiffness or any pure matrix data.


RE: Is AUTOSPC the same as “Automatic constraints”?

Strike that question. I just saw your previous post and I will answer it there.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close